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GStreamer 0.10 Core Reference Manual | ![]() |
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#include <gst/gst.h> GstTask; void (*GstTaskFunction) (void *data); enum GstTaskState; #define GST_TASK_BROADCAST (task) #define GST_TASK_GET_COND (task) #define GST_TASK_GET_LOCK (task) #define GST_TASK_SIGNAL (task) #define GST_TASK_STATE (task) #define GST_TASK_WAIT (task) void gst_task_cleanup_all (void); GstTask* gst_task_create (GstTaskFunction func, gpointer data); GstTaskState gst_task_get_state (GstTask *task); gboolean gst_task_join (GstTask *task); gboolean gst_task_pause (GstTask *task); void gst_task_set_lock (GstTask *task, GStaticRecMutex *mutex); gboolean gst_task_start (GstTask *task); gboolean gst_task_stop (GstTask *task);
GstTask is used by GstElement and GstPad to provide the data passing threads in a GstPipeline.
A GstPad will typically start a GstTask to push or pull data to/from the peer pads. Most source elements start a GstTask to push data. In some cases a demuxer element can start a GstTask to pull data from a peer element. This is typically done when the demuxer can perform random access on the upstream peer element for improved performance.
Although convenience functions exist on GstPad to start/pause/stop tasks, it might sometimes be needed to create a GstTask manually if it is not related to a GstPad.
Before the GstTask can be run, it needs a GStaticRecMutex that can be set with gst_task_set_lock().
The task can be started, paused and stopped with gst_task_start(), gst_task_pause() and gst_task_stop() respectively.
A GstTask will repeadedly call the GstTaskFunction with the user data that was provided when creating the task with gst_task_create(). Before calling the function it will acquire the provided lock.
Stopping a task with gst_task_stop() will not immediatly make sure the task is not running anymore. Use gst_task_join() to make sure the task is completely stopped and the thread is stopped.
After creating a GstTask, use gst_object_unref() to free its resources. This can only be done it the task is not running anymore.
Last reviewed on 2006-02-13 (0.10.4)
typedef struct { GstTaskState state; GCond *cond; GStaticRecMutex *lock; GstTaskFunction func; gpointer data; gboolean running; } GstTask;
The GstTask object.
GstTaskState state; | the state of the task |
GCond *cond; | used to pause/resume the task |
GStaticRecMutex *lock; | The lock taken when iterating the taskfunction |
GstTaskFunction func; | the function executed by this task |
gpointer data; | data passed to the task function |
gboolean running; | a flag indicating that the task is running. |
gpointer _gst_reserved[GST_PADDING + 0]; |
void (*GstTaskFunction) (void *data);
A function that will repeadedly be called in the thread created by a GstTask.
data : | user data passed to the function |
typedef enum { GST_TASK_STARTED, GST_TASK_STOPPED, GST_TASK_PAUSED } GstTaskState;
The different states a task can be in
#define GST_TASK_BROADCAST(task) g_cond_breadcast(GST_TASK_GET_COND (task))
Send a broadcast signal to all waiting task conds
task : | Task to broadcast |
#define GST_TASK_GET_COND(task) (GST_TASK_CAST(task)->cond)
Get access to the cond of the task.
task : | Task to get the cond of |
#define GST_TASK_GET_LOCK(task) (GST_TASK_CAST(task)->lock)
Get access to the task lock.
task : | Task to get the lock of |
#define GST_TASK_SIGNAL(task) g_cond_signal(GST_TASK_GET_COND (task))
Signal the task cond
task : | Task to signal |
#define GST_TASK_STATE(task) (GST_TASK_CAST(task)->state)
Get access to the state of the task.
task : | Task to get the state of |
#define GST_TASK_WAIT(task) g_cond_wait(GST_TASK_GET_COND (task), GST_OBJECT_GET_LOCK (task))
Wait for the task cond to be signalled
task : | Task to wait for |
void gst_task_cleanup_all (void);
Wait for all tasks to be stopped. This is mainly used internally to ensure proper cleanup of internal datastructures in testsuites.
MT safe.
GstTask* gst_task_create (GstTaskFunction func, gpointer data);
Create a new Task that will repeadedly call the provided func with data as a parameter. Typically the task will run in a new thread.
The function cannot be changed after the task has been created. You must create a new GstTask to change the function.
func : | The GstTaskFunction to use |
data : | User data to pass to func |
Returns : | A new GstTask. MT safe. |
GstTaskState gst_task_get_state (GstTask *task);
Get the current state of the task.
task : | The GstTask to query |
Returns : | The GstTaskState of the task MT safe. |
gboolean gst_task_join (GstTask *task);
Joins task. After this call, it is safe to unref the task and clean up the lock set with gst_task_set_lock().
The task will automatically be stopped with this call.
This function cannot be called from within a task function as this would cause a deadlock. The function will detect this and print a g_warning.
task : | The GstTask to join |
Returns : | TRUE if the task could be joined. MT safe. |
gboolean gst_task_pause (GstTask *task);
Pauses task. This method can also be called on a task in the stopped state, in which case a thread will be started and will remain in the paused state. This function does not wait for the task to complete the paused state.
task : | The GstTask to pause |
Returns : | TRUE if the task could be paused. MT safe. |
void gst_task_set_lock (GstTask *task, GStaticRecMutex *mutex);
Set the mutex used by the task. The mutex will be acquired before calling the GstTaskFunction.
This function has to be called before calling gst_task_pause() or gst_task_start().
MT safe.
task : | The GstTask to use |
mutex : | The GMutex to use |
gboolean gst_task_start (GstTask *task);
Starts task. The task must have a lock associated with it using gst_task_set_lock() or thsi function will return FALSE.
task : | The GstTask to start |
Returns : | TRUE if the task could be started. MT safe. |
gboolean gst_task_stop (GstTask *task);
Stops task. This method merely schedules the task to stop and will not wait for the task to have completely stopped. Use gst_task_join() to stop and wait for completion.
task : | The GstTask to stop |
Returns : | TRUE if the task could be stopped. MT safe. |